1. Field of the Invention
The present invention relates to an injection mold device for injecting a molten resin thereinto and molding it into a thick-walled product with high accuracy.
2. Description of the Related Art
In the case of producing a thick-walled part, such as a plastic lens, by injection molding, a cooling process is necessary for the purpose of preventing shrinkage or deformation, which inconveniently prolongs the molding cycle time. As a method of molding a thick-walled part in a short molding cycle time without causing shrinkage or deformation, an injection molding method disclosed in Japanese Patent Laid-Open No. 64-36421 is known. In this injection molding method, after a pair of mold pieces removably provided on templates on the movable side and the fixed side is clamped together by an injection molding machine, the pair of mold pieces is clamped together by a U-shaped mold clamping member and then heated to a temperature above the glass transition temperature of the resin. After injecting a molten resin into the mold, the gate is closed so as to gradually cool the mold to the thermal transformation temperature, and the mold-clamping member is removed from the injection molding machine while the pair of mold members is held in the mold-clamped state. The mold is moved to a place outside of the injection molding machine to be cooled. During this time, other mold pieces are manually set on each template of the molding machine, a molten resin is injected and then gradually cooled in the same way as described above. The mold pieces are then manually removed from the mold-clamping member and manually moved to the outside of the molding machine to be cooled. By this method, the molding cycle is repeated by using a plurality of molds. In the above-described conventional molding method, however, it is necessary to remove the mold from the mold-clamping member in the cooling process and to set another mold in the molding machine during the cooling process. The manual movement, setting and removal of a mold are troublesome, and the change-over of molds is inconvenient and time consuming.